The present invention relates to an electronically controlled shift system for manual transmissions of a motor vehicle. More particularly, the present invention relates to an electronically controlled shift system for determining a synchronization force and for applying variable force levels to engage a selected gear of a synchronized manual transmission.
Electronics have been integrated into many automotive systems ever since the benefits of these systems were realized. In the drive train area, electronics have greatly enhanced engine control systems, automatic transmission systems (hydraulic transmissions) and four wheel drive systems. Past history has also shown the application of electronics into clutch systems. Many of these systems initially were unsuccessful due to the lack of power in the controls area. Since the advent of the microprocessor and other advanced electronic technologies, many systems that were formerly not technologically feasible, are now realizable. Automatic clutch systems are now production items on several European small car platforms.
The manual transmission has also been the target of the electronics revolution, but only in recent times. While purely mechanical manual transmissions are still dominant, some automated manual transmissions are making appearances into the marketplace. Most of this development has centered in Europe where the driving factors, including fuel economy and emissions, are most relevant.
Accordingly, a need exists for a transmission whose shift actuation is entirely electronically controlled, such that there is no mechanical link between the driver and the gearbox (excluding the clutch). Shifting of the gearbox is to be commanded by an electronic shift lever accessible to the driver. Advantages of this electronically controlled shift system include reduced noise and vibration in the passenger compartment, increased protection from driver shifting errors, easier tailoring of shift lever feel, easier location of the shift lever and a reduction in the gearbox component count. Moreover, an electronically controlled shift system provides greater control of gear engagement, such that optimum shift force can be determined at shift time, shift efforts can compensate for engine temperature and variable shift forces can be applied to shift gears.